Pelinobius muticus belongs to the subfamily Eumenophorinae. (Hysterocrates spp. and Monocentropus balfouri are also in this subfamily.) Phylogenetics assigns the Eumenophorinae the first branch in the theraphosid family tree, making P. muticus among the most primitive, evolutionarily speaking.
P. muticus comes from southern Kenya and northern Tanzania. It has been in the hobby for decades, known to old timers as Citharischius crawshayi. A large, burrowing spider, P. muticus is widely known for slow growth and difficulty breeding. Curiously, from the same geographic region come fast-growing and easy-to-breed Pterinochilus spp. (e.g. murinus and chordatus). Field-collected juveniles and larger sizes of P. muticus were once common in the market. Spiderlings, possibly captive-hatched, and small field-collected juveniles are currently the main forms available.
In the wild, P. muticus is found in burrows up to 50 cm deep, at the base of Acacia scrub bushes . One website claims 2 m burrows, unverified to our knowledge. In captivity, P. muticus will burrow to the bottom of any substrate depth commonly provided and will excavate a cavity up to twice its height. From a keeping perspective, P. muticus requirements are the same as those for Hysterocrates spp. They both do best with a continuous source of water, in the form of a water dish, humidity, or both. Substrate dampening can also be used, with care taken to avoid uniform wetness. Rare reports of successful breeding exist , [LINK].
The following video by Guy Tansley et al shows P. muticus in the wild: [LINK].
The photo above shows an adult female [courtesy
 A. M. Smith (1990) Baboon spiders, tarantulas of Africa and the Middle East. London, Fitzgerald.
 G. Tansley (2001) Citharischius crawshayi – the king baboon – first successful UK breeding? J. Br. Tarantula Soc. 16(2): 42–43.